lwline_split_by_line()

static LWGEOM * lwline_split_by_line ( const LWLINE *  lwgeom_in, const LWGEOM *  blade_in  )

static

Definition at line 43 of file lwgeom_geos_split.c.

{
        LWGEOM** components;
        LWGEOM* diff;
        LWCOLLECTION* out;
        GEOSGeometry* gdiff; /* difference */
        GEOSGeometry* g1;
        GEOSGeometry* g2;
        int ret;
 
        /* ASSERT blade_in is LINE or MULTILINE */
        assert (blade_in->type == LINETYPE ||
                blade_in->type == MULTILINETYPE ||
                blade_in->type == POLYGONTYPE ||
                blade_in->type == MULTIPOLYGONTYPE );
 
        /* Possible outcomes:
         *
         *  1. The lines do not cross or overlap
         *      -> Return a collection with single element
         *  2. The lines cross
         *      -> Return a collection of all elements resulting from the split
         */
 
        initGEOS(lwgeom_geos_error, lwgeom_geos_error);
 
        g1 = LWGEOM2GEOS((LWGEOM*)lwline_in, 0);
        if ( ! g1 )
        {
                lwerror("LWGEOM2GEOS: %s", lwgeom_geos_errmsg);
                return NULL;
        }
        g2 = LWGEOM2GEOS(blade_in, 0);
        if ( ! g2 )
        {
                GEOSGeom_destroy(g1);
                lwerror("LWGEOM2GEOS: %s", lwgeom_geos_errmsg);
                return NULL;
        }
 
        /* If blade is a polygon, pick its boundary */
        if ( blade_in->type == POLYGONTYPE || blade_in->type == MULTIPOLYGONTYPE )
        {
                gdiff = GEOSBoundary(g2);
                GEOSGeom_destroy(g2);
                if ( ! gdiff )
                {
                        GEOSGeom_destroy(g1);
                        lwerror("GEOSBoundary: %s", lwgeom_geos_errmsg);
                        return NULL;
                }
                g2 = gdiff; gdiff = NULL;
        }
 
        /* If interior intersection is linear we can't split */
        ret = GEOSRelatePattern(g1, g2, "1********");
        if ( 2 == ret )
        {
                lwerror("GEOSRelatePattern: %s", lwgeom_geos_errmsg);
                GEOSGeom_destroy(g1);
                GEOSGeom_destroy(g2);
                return NULL;
        }
        if ( ret )
        {
                GEOSGeom_destroy(g1);
                GEOSGeom_destroy(g2);
                lwerror("Splitter line has linear intersection with input");
                return NULL;
        }
 
 
        gdiff = GEOSDifference(g1,g2);
        GEOSGeom_destroy(g1);
        GEOSGeom_destroy(g2);
        if (gdiff == NULL)
        {
                lwerror("GEOSDifference: %s", lwgeom_geos_errmsg);
                return NULL;
        }
 
        diff = GEOS2LWGEOM(gdiff, FLAGS_GET_Z(lwline_in->flags));
        GEOSGeom_destroy(gdiff);
        if (NULL == diff)
        {
                lwerror("GEOS2LWGEOM: %s", lwgeom_geos_errmsg);
                return NULL;
        }
 
        out = lwgeom_as_lwcollection(diff);
        if ( ! out )
        {
                components = lwalloc(sizeof(LWGEOM*)*1);
                components[0] = diff;
                out = lwcollection_construct(COLLECTIONTYPE, lwline_in->srid,
                                             NULL, 1, components);
        }
        else
        {
          /* Set SRID */
                lwgeom_set_srid((LWGEOM*)out, lwline_in->srid);
          /* Force collection type */
          out->type = COLLECTIONTYPE;
        }
 
 
        return (LWGEOM*)out;
}

References COLLECTIONTYPE, LWLINE::flags, FLAGS_GET_Z, LINETYPE, lwalloc(), lwcollection_construct(), lwerror(), LWGEOM2GEOS(), lwgeom_as_lwcollection(), lwgeom_geos_errmsg, lwgeom_geos_error(), lwgeom_set_srid(), MULTILINETYPE, MULTIPOLYGONTYPE, POLYGONTYPE, LWLINE::srid, and LWGEOM::type.

Referenced by lwline_split().

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